1. Field
The presently disclosed subject matter relates to methods and systems for removing pollutant gases from the exhaust gas stream formed by a combustion process, such as internal combustion engines, furnaces, power plants, and so forth. Particularly, the disclosed subject matter is related to the use of activated-carbon-supported metal catalysts for the selective catalytic reduction of nitrogen oxides (NOx) from exhaust gases resulting directly or indirectly from a combustion process in the exploration, production, refining, manufacture, supply, transport, formulation or blending of petroleum, petrochemicals or the direct products thereof.
2. Description of Related Art
Combustion devices in commercial applications, such as those in the petroleum and petrochemical processing field, which includes the exploration, production, refining, manufacture, supply, transport, formulation or blending of petroleum, petrochemicals, or the direct products thereof, are a source of NOx emissions. A continuing effort has been made over the years to develop methods and systems to remove pollutant gases from exhaust gases produced by combustion unit operations.
Increasingly stringent environmental regulations have been enacted world-wide in an effort to reduce the emission of pollutant gases into the atmosphere from combustion equipment used by numerous unit operations within a commercial operation. Of particular interest is the production of nitrogen oxides (NOx).
Nitrogen oxides (NOx) are produced, for example, when nitrogen reacts with oxygen within a combustion chamber under high temperature and pressure conditions. NOx can also be produced, for example, in fluid catalytic converters (FCCs) and furnaces due to combustion of nitrogen from FCC feeds, heating oil, and/or fuel oil. Such nitrogen oxides can include either one or a combination of nitrogen monoxide and nitrogen dioxide.
Various selective catalytic reduction (SCR) methods have been developed in an effort to reduce NOx emissions. SCR is a catalytic technique to convert NOx to diatomic nitrogen, N2, and water, H2O. Typically, a fluid reductant—such as anhydrous ammonia, aqueous ammonia or urea—is added to a stream of exhaust gas and absorbed onto a catalyst.
However, such known techniques can be expensive to operate and/or may have limited capacity or efficiency. As such, there is a continued need for improved methods and apparatus for removing NOx from the exhaust gas stream of a combustion device, particularly those found in chemical processing and/or petrochemical refining operations.